This invention relates to disposable absorbent articles and more particularly to improvements in adult incontinence briefs of the kind utilizing fastening tapes with pressure-sensitive adhesive for securing parts of the brief together in order to fit the diaper to the person.
Disposable absorbent articles, such as infant diapers and adult incontinence products, are used to absorb body fluids and waste materials of infants, children and adults. These products are provided, for example, as briefs or undergarments, and have a moisture absorbent pad covered on one side by a moisture-permeable, body-contacting cover sheet and on the other side by a moisture-impermeable or hydrophobic backing sheet. Typically, the disposable absorbent article is fitted to the wearer by two or more fastening tapes, which are permanently connected to, and extend from, the outside surface of the backing sheet and are adhesively secured to areas of the outside surface of the backing sheet known variously as xe2x80x9ctarget zonesxe2x80x9d or xe2x80x9clanding zones.xe2x80x9d
After the disposable absorbent article is initially secured on the wearer, adjustment is often necessary in order to obtain a proper fit. Thus, after the fastening tapes are initially secured to the landing zone, detachment and reattachment of the tapes are required in order to carry out the desired adjustment. A backing sheet which is too thin or weak will rip or become damaged when the fastening tape is removed. Thus, to achieve the necessary strength to permit tape removal and reattachment, the backing sheets of disposable absorbent articles are generally made relatively thick. For example, a backing sheet made from a polyethylene film having a uniform thickness of 1.1 mils (0.0011 inch or 0.028 mm) has been found to provide the required strength, even at the low end of the film thickness range, to permit tape removal and reattachment without causing excessive damage to the backing sheet. However, the thickness of the backing material is important only in order to avoid tearing the backing material when the tape is removed from it. The use of thick backing sheet material results in significant material costs, and thus, the backing sheet is not a xe2x80x9cvalue-addingxe2x80x9d feature.
As an alternative to relatively thick and expensive backing sheet materials, backing sheets have been provided with reinforced landing zone areas to permit removal and reattachment of the fastening tapes without ripping or otherwise damaging the backing sheet. For example, U.S. Pat. No. 4,911,702 to O""Leary et al. discloses a disposable absorbent adult brief having a backing film with two xe2x80x9ctarget tapesxe2x80x9d on a backing having a thickness in the range of 1.0 to 1.3 mil. FIG. 2 of the O""Leary patent illustrates a prior art adult brief having four attachment tabs and two target tapes, the stated purpose of which is to serve as attachment points for the attachment tabs so that, if desired, they may be repositioned without tearing the thin polyethylene backing film.
U.S. Pat. Nos. 5,370,639, 5,024,672 and 5,236,429, to Widlund, disclose a disposable diaper having a polyethylene backing film onto which a plastic strip is glued, and to which pressure-adhesive tapes are secured.
U.S. Pat. No. 5,026,446 to Johnston et al. discloses a method of manufacturing a disposable diaper having a target strip. The target strips are made of high-strength thermoplastic films such as biaxially oriented polypropylene film or biaxially oriented poly (ethylene terephthalate) film having a thickness of 0.6 to 1.6 mil. A roll of pressure-sensitive adhesive tape is first fed through a metal roll and a counter rotating abrasive brush and is then fed onto a vacuum wheel where it is cut into strips by a rotary cutter. Each strip is adhered to a diaper web with pressure applied by a rubber pad on a steel roll.
U.S. Pat. No. 4,710,190 to Wood et al. discloses a disposable diaper having a reinforcement strip made of polypropylene or poly (ethylene terephthalate) film having a thickness of 0.4 to 3.0 mil. A bonding layer secures the strip to the backing film when the strip and backing film are applied with pressure and heat, such as, by a heating roll.
U.S. Pat. Nos. 4,753,649 to Pazdernik; 5,106,383 to Mulder et al., U.S. Pat. No. 5,720,739 to Hilston et al., U.S. Pat. No. 5,649,921 to Arakawa et al. and U.S. Pat. No. 5,599,620 to Huskey disclose various other disposable diapers having reinforcement strips adhesively secured to backing films. U.S. Pat. No. 5,690,628 to Huskey et al., U.S. Pat. No. 5,527,305 to Goulait et al.; 5,061,262 to Chen et al., U.S. Pat. No. 5,275,588 to Matsumoto et al. and U.S. Pat. No. 5,722,969 to Ito et al. disclose various other disposable diapers having reinforced landing zones.
Although the aforementioned disposable absorbent articles having reinforced landing zones, and their methods of manufacture, may be satisfactory for their intended purposes, there remains a need for an improved disposable absorbent article which permits tape removal and re-fastening and which can be produced at lower cost. There is also a need for an improved, more efficient and cost-effective method of producing a disposable absorbent article having a reinforced landing zone.
The principal object of this invention is to provide a disposable absorbent article, adapted to be worn on the person, which has a reinforced landing zone permitting tape removal and re-fastening, and which can be produced at a very low cost. An additional object of this invention is to provide an efficient and cost-effective method of producing a disposable absorbent article having a reinforced landing zone.
The invention addresses the foregoing objects in a disposable absorbent article comprising a thin, liquid-impermeable backing sheet having a uniform thickness, preferably in the range of 0.3 to 0.9 mil, and opposite inner and outer faces. An absorbent layer is secured to the inner face, and tapes, secured to first and second areas on the outer face of the backing sheet have portions extending therefrom coated by a pressure-sensitive adhesive. The pressure-sensitive adhesive is sufficiently aggressive and the backing sheet is sufficiently thin, that if the tapes were adhered by the adhesive directly to the outer face of the backing sheet, they could not be removed consistently from the backing sheet without ripping the backing sheet. Reinforcement sheets, which are preferably of uniform thickness in the range of about 0.2 to 0.9 mil, are secured to the outer face of the backing sheet to establish landing zones for attachment of the adhesive-coated portions of the tapes. These reinforcement sheets are secured to the outer face of the backing sheet respectively over third and fourth, preferably rectangular, areas. The reinforcement sheets are secured respectively to the third and fourth areas of the outer face of the backing sheet by layers of adhesive which are uninterrupted widthwise and lengthwise over each of the third and fourth areas.
A key to the achievement of highly superior results with the invention is the application of the layer or layers of adhesive to the reinforcement sheets by slot coating. Slot coating produces the uninterrupted area coverage, and thereby prevents gaps in the adhesive layer which could result in ripping of the reinforcement sheets or separation of the reinforcement sheets from the backing sheet. It also enhances efficiency in adhesive usage, produces a uniform adhesive coating thickness, and provides well-defined margins along opposite edges of the reinforcement strips, thereby avoiding areas of exposed adhesive which could result in portions of the article adhering to one another or to other, similar articles.
Another key to the achievement of highly superior results with the invention is the application of hot melt adhesive to a thin, heat-sensitive polymeric film. One method to achieve this is first to xe2x80x9cslot coatxe2x80x9d the hot melt adhesive to a low friction, smooth roll (made of PTFE, or having a silicone or PTFE coating), which is cooled as well. Rolls of this kind are known as xe2x80x9cchill rolls.xe2x80x9d The chill roll is then rotated to transfer coat the lower temperature hot-melt adhesive to a polymeric film. The hot melt adhesive, which is a pressure-sensitive adhesive, sticks to the higher friction polymeric film and is thus transferred completely from the chill roll to the film.